1. Field of the Invention
This application relates to medical catheters for use in intravascular procedures, and more particularly, to a catheter having improved flexibility at its distal end.
2. Description of the Related Art
Medical catheters such as balloon catheters have been proven efficacious in treating a wide variety of blood vessel disorders. Moreover, these types of catheters have permitted clinicians to treat disorders with minimally invasive procedures that, in the past, would have required complex and perhaps life-threatening surgeries. For example, balloon angioplasty is now a common procedure to alleviate stenotic lesions (i.e., clogged arteries) in blood vessels, thereby reducing the need for heart bypass operations.
Because medical catheters must be passed through a tortuous blood vessel network to reach the intended treatment site, it is desirable that the catheter be fairly flexible, especially at the distal end. However, the distal end must, not be so flexible that it tends to bend back upon itself when the clinician advances the catheter distal end through the patient.
One method of imparting desired flexibility characteristics: to a catheter has been to incorporate a xe2x80x9ccore wirexe2x80x9d into the distal end of the catheter. A core wire is a wire that extends from the distal end of the catheter body, providing structural support to the distal end to prevent prolapse, bend backs or kinks during catheter advancement. Furthermore, the core wire is also flexible, such that the catheter""s distal end may navigate tortuous blood vessel, networks or other body cavities.
However, conventional core wires often do not offer an ideal flexibility profile for the distal end of a catheter. For instance, when a core wire is mounted inside the distal end of a catheter body, because the catheter body is relatively rigid compared to the relatively flexible core wire, an abrupt transition in flexibility is produced between the core wire and the catheter body. This transition is undesirable because when the catheter is advanced through a tortuous pathway, the catheter may experience a sharp bend at the transition point. This makes it difficult for the catheter to navigate the vessel and increases the likelihood of damage to the vessel.
Moreover, a catheter carrying a balloon or other expandable member on its distal end experiences particular problems related to the flexibility profile of the device. For instance, with many balloon catheters, the transition in flexibility between the catheter portion carrying the balloon and the wire extending past the distal end of the balloon is often too abrupt, leading to the problem that when the catheter is advanced through a blood vessel, the flexible wire is capable of navigating blood vessel turns, but the stiffer portion where the balloon is located cannot. This causes stabbing of the balloon into the walls of the vessel during navigation of tight turns.
Problems also arise in these devices with regard to the dimensional range of the balloon. Balloons mounted on the distal end of the catheters have a tendency to expand not only radially but also longitudinally upon inflation. Depending on the balloon material used, the balloon length may expand minimally (e.g., polyethylene terephthalate) or extensively (e.g., latex or C-Flex). For example, an unmounted C-Flex balloon with a length of about 9 mm has been found to expand longitudinally anywhere from 2 to 20 mm upon inflation. Thus, when the catheters and/or core wires to which these balloons are mounted are too rigid, inflation of the balloon may cause bowing of the catheter and/or core wire and other undesired effects.
Furthermore, balloon centering and rupture are also affected by the flexibility profile of the catheter. In particular, when balloon expansion is limited by the rigidity of the catheter and/or core wire, the balloon cannot uniformly expand. This causes an uneven distribution of stresses within the balloon which causes the balloon to become poorly centered. Moreover, the uneven distribution of stresses can create stress concentration points leading to diminished fatigue life and ultimately quicker balloon failure.
Accordingly, what is needed is an improved balloon catheter offering desired flexibility characteristics around and within the balloon to improve balloon range, centering and rupture properties. What is also needed is a catheter having improved flexibility to exhibit a better transition from the proximal end to the distal end of the catheter.
The present invention solves the needs described above by providing a catheter having an improved flexibility profile in and about its distal end. In particular, for a catheter carrying a balloon on its distal end, the preferred embodiments of the present invention improve the transition and flexibility of the catheter in and around the area where the balloon is mounted. In one aspect of the present invention, a catheter is provided comprising an elongate body having a proximal end and a distal end. At least one connecting wire having a proximal end and a distal end is provided, the proximal end of the wire being mounted to the distal end of the elongate body and the distal end of the wire extending past the distal end of the elongate body. A core wire is provided having a proximal end connected to the distal end of the connecting wire and extending distally therefrom. In one embodiment, because the core wire is not directly attached to the catheter body, a transition region is provided between the catheter body and the core wire to give the catheter a gradually increasing flexibility.
In another aspect of the present invention, a medical device is provided comprising an elongate body having a proximal end and a distal end. An expandable member is mounted to the distal end of the elongate body. A core wire is provided lying along substantially the same longitudinal axis as the elongate body, the core wire having a proximal end and a distal end. The proximal end of the core wire is located within the expandable member and is spaced distally from the distal end of the elongate body. Means are provided for connecting the elongate body to the core wire.
In another aspect of the present invention, a balloon catheter is provided comprising an elongate tubular body having a proximal end and a distal end and a lumen extending therethrough. An inflatable balloon is mounted over the distal end of the tubular body. A core wire lies along substantially the same longitudinal axis as the tubular body, the core wire having a proximal end and a distal end. The proximal end of the core wire is distally spaced from the distal end of the tubular body outside of the lumen. A plurality of connecting wires connects the distal end of the tubular body to the core wire.
In another aspect of the present invention, a catheter is provided comprising an elongate tubular body having a proximal end and a distal end and a lumen extending therethrough. A core wire having a proximal end and a distal end is provided, wherein the proximal end of the core wire extends into the lumen of the tubular body and the distal end extends distally away from the tubular body. A portion of the core wire is positioned coaxially inside the lumen to create an annular space between the core wire and the tubular body. The annular space extends around the core wire over the entire length of that portion of the core wire inside the lumen. An expandable member is provided having a proximal end mounted over the distal end of the tubular body and a distal end mounted over the core wire distal to the tubular body.
This embodiment in effect allows the proximal end to xe2x80x9cfloatxe2x80x9d within the tubular body, such that when the catheter is advanced through the vasculature of a patient, the core wire may move longitudinally within the tubular body. This longitudinal movement creates the effect that the catheter is gradually increasing in flexibility between the tubular body and the core wire, because when the distal end of the catheter bends, the core wire moves distally out of the catheter to make the bend more gradual. Furthermore, when a balloon or other expandable device is mounted between the tubular body and the core wire, the longitudinal movement allowed by the floating core wire further accommodates any longitudinal expansion by the balloon or expandable device upon actuation.
In another aspect of the present invention, a catheter is provided comprising an elongate tubular body having a proximal end and a distal end and a lumen extending therethrough. A core wire having a proximal end and a distal end is provided, the proximal end of the core wire extending into the lumen at the distal end but remaining unattached thereto. A flexible member connects the tubular body to the core wire.
In another aspect of the present invention, a catheter is provided comprising an elongate tubular body having a proximal section and a distal section and a lumen extending therethrough. An expandable member is mounted to the distal section. The distal section is configured to axially expand in response to expansion of the expandable member.
In another aspect of the present invention, a catheter is provided comprising an elongate tubular body having a proximal end and a distal end and a lumen extending therethrough. An expandable member is mounted to the distal end of the tubular body. The tubular body has a coiled section that extends at least partially within the expandable member to provide the tubular body with longitudinal flexibility upon actuation of the expandable member.
In another aspect of the present invention, a catheter is provided comprising an elongate body having a proximal end and a distal end. An expandable member is mounted to the distal end. The elongate body receives cuts at least partially proximal to the expandable member.
In another aspect of the present invention, a catheter is provided comprising an elongate assembly having a distal portion. A balloon is mounted on the distal portion of the elongate assembly, the balloon being comprised of a sheet material attached to the elongate assembly at spaced locations such that the sheet material between the spaced locations expands outwardly in response to inflation pressure to inflate the balloon. The elongate assembly is axially expandable between the spaced locations to accommodate changes in the balloon shape as the balloon is inflated, whereby stresses in the balloon are reduced.
In another aspect of the present invention, a method is provided, comprising providing a catheter comprised of an elongate assembly having a balloon thereon. The balloon is inflated in a body lumen. A portion of the elongate assembly is axially elongated within the balloon during inflation of the balloon to reduce stresses on the balloon material.